The present invention relates to a pressure responsive electric switch incorporating a diaphragm, and particularly to a plug type switch adapted for use in a circuit for an oil pressure warning light.
Switches of the type dscribed herein employ a diaphragm which separates the electrical contact surfaces from the fluid whose pressure is being sensed. These switches were developed in response to a need for a switch where the contact surfaces would not be contaminated by the fluid, which would adversely affect the switching. Most such switches in the prior art included several contact members in addition to a helical spring. See, e.g., U.S. Pat. No. 3,319,024. A simplification over most prior art is described in U.S. Pat. No. 3,555,220, which employs two stamped and formed sheet metal parts as contacts, one of which is stationary and the other resiliently movable to make or break contact with the stationary contact in response to movement by the diaphragm. This represents a savings in manufacturing costs due to the number and simplicity of parts, and likewise reduces the probability of failure.
The instant invention is simplest yet insofar as it employs a single stamped and formed sheet metal contact member resiliently movable to make or break contact with a conductive body member in response to movement by the diaphragm. The contact member is a strip formed with a spade terminal at one end which is inserted through a cap fixed to a conductive body member and a spring portion with a free end arranged in proximity to a contact point on the body member. The spring portion is acted on by a protrusion on the diaphragm mounted adjacent thereto on a shoulder in a passage through the body member. Over pressure protection is provided to prevent changing calibration of the spring portion.
It is thus an object of the present invention to provide a pressure switch with a minimum of parts, which are simple and economical to manufacture.
This and other objects achieved by the present invention will be apparent on considering the drawings and description which follow.